Some front part structures of vehicle bodies are provided with front side frames curving to the left and right of the engine disposed to the front of the passenger compartment. The front side frame is designed to minimize deformation during a collision, and is composed of an axial load receiving member comprising a first ridge line extending rectilinearly across the entire length in the lengthwise direction, and a moment receiving member branched from an approximately center section in the longitudinal direction of the first ridge line, and comprising a second ridge line which curves inwardly in the widthwise direction of the vehicle toward the rear of the vehicle (see Patent Literature 1, for example).
However, the axial load receiving member and the moment receiving member of the front side frame disclosed in Patent Literature 1 have shapes that taper from a thin tip to a thick base, and an associated problem is high production cost of the dies employed during plastic working of these. Another problem is a difficultly in handling, due to the thin tip sections being readily deformed and respectively different in size. Also, when the axial load receiving member and the moment receiving member are assembled together, positioning of the members is difficult, and workability is poor.